Diamines are especially valuable for curing various polyurethanes, particularly isocyanate terminated polyurethane prepolymers. Aromatic diamine curatives are particularly valuable for curing aromatic isocyanate-terminated prepolymers (to provide polyurethanes having enhanced age resistance in the presence of moisture and various liquid hydrocarbon fuels). However, heretofore, aromatic diamines typically react too fast with aromatic isocyanate-terminated prepolymers and therefore seriously inhibit their commercial significance. The 4,4'-methylene bis(2-chloroaniline), sometimes referred to as MOCA, a well known diamine, is slower reacting at room temperature and should be considered an exception to such typical fast reacting aromatic diamines.
For the MOCA cured aromatic NCO-terminated prepolymers a catalyst is many times used to shorten the reaction time and enhance their commercial significance especially in the preparation of urethane films in solution systems.
Therefore, it is an object of this invention to provide aromatic diamines suitable for curing aromatic isocyanate-terminated polyurethane prepolymers, methods of preparing such aromatic diamines and isocyanate-terminated polyurethanes extended with aromatic diamines.